The microelectronics industry is highly competitive and most microelectronics manufacturers are highly sensitive to quality and cost considerations. Most microelectronics manufacturers require that suppliers of microelectronic components test performance of each microelectronic component before shipment to minimize the manufacturer's product losses. Microelectronic components are commonly tested by establishing temporary electrical connections between a test system and electrical terminals on the microelectronic component.
One way of establishing a temporary electrical connection between the test system and the terminals on the component employs cantilevered wire probes. Such wire probes employ a stiff wire tip at the end of an elongate arm. Cantilevered wire probes are useful in some applications, e.g., in testing devices with bond pads spaced well apart from one another, but these probes do have some limitations. If the microelectronic component is a “bumped” chip having a solder ball attached to each of a series of bond pads, the mechanical force of the probe against the solder ball can damage the solder ball or the connection between the solder ball and the bond pad. This can lead to faulty electrical connections in future manufacturing steps. The minimum spacing of cantilevered wire probes is also somewhat constrained, limiting their use in testing microelectronic components with contacts that are close to one another, such as in fine ball grid array (FBGA) chips.
Another common way to temporarily electrically connect a microelectronic component to a test system employs a test card with rigid contacts. These contacts may be adapted to rigidly abut the component's contacts, e.g., a bond pad of an unbumped chip or contact solder balls on a bumped chip. Planarity of both the test card and the component contacts is of critical importance when testing unbumped chips. To ensure that the test card adequately contacts each of the bond pads, the microelectronic component must be urged toward the test card with some force. This could damage the microelectronic component under test. When testing bumped microelectronic components, the contacts on the test card may be specifically adapted to receive solder balls instead of contacting a relatively flat bond pad. These solder-specific contacts commonly scratch, squeeze, or otherwise deform the solder balls to ensure good electrical contact between the solder balls and the test card contacts. This can exert undue stress on the solder balls, damaging the solder balls or their connection to the underlying bond pads.
The trend in the industry is for terminals on microelectronic components to be spaced closer and closer together. Many microelectronic components, e.g., FBGA chips, have solder ball pitches (i.e., the distance from the center of one solder ball to the center of the next adjacent solder ball) of 0.8 millimeters or less; the solder balls on such contacts are often 0.3 millimeters or less in diameter. These small solder balls are very susceptible to damage when being deformed by a mechanical interface on a conventional test card. Test card manufacturers also are finding it increasingly difficult to position the terminals close enough to one another to permit testing of fine-pitch microelectronic components.